1. Field of the Invention
The invention relates to a low power, point to multipoint, multi-function cellular television system.
2. Description of Related Art
Low power television has been the object of many recent investigations. A useful discussion can be found in the article entitled "Low-Power Television--Short Range, Low Cost TV Stations are in the Offing as the FCC Prepares to Establish Broadcast Requirements" that appeared in the IEEE Spectrum, Pages 54 through 59, June 1982.
Multi-point radio communication is discussed in some U.S. Patents, including U.S. Pat. No. 4,528,656. There are also existing applications for polarization diversity between transmitting and receiving antennas. It is known that two way satellite communications often involves the use of vertically or horizontally polarized signals which communicate respectively with vertically and horizontally polarized signals from earth. There also exists some limited circumstances where individual horizontal and vertical diversity is employed. See for example, U.S. Pat. No. 2,288,802 which describes a system of transmission between two stations wherein vertically polarized waves travel in one direction and horizontal polarized waves travel in another. However, it should be noted that the concept of polarization diversity is normally limited to two transmitting stations and not to arrays of receiving and transmitting antennas.
The use of directional antennas is found in certain contexts. Note, for example, U.S. Pat. No. 3,041,450 which describes the use of a directional receiver for receiving a signal from an omni-directional transmitting antenna. Other patents that discuss polarized modulation or the use of horizontal vs. vertical polarization in the context of radio transmissions include U.S. Pat. Nos. 2,992,427; 3,882,393; 4,220,923; 4,321,705 and 4,521,878.
U.S. Pat. No. 4,495,648 is of possible relevance in that it appears to disclose a concept for monitoring a radio signal at a distant location and then modifying the transmission to adjust the output power of the originating transmitter. Phase-lock loops are occasionally used in the context of radio receivers. Note for example, U.S. Pat. No. 4,228,540.
One major problem associated with low power television and high frequency transmissions is fading due to rainfall and the like. A brief discussion of that problem is found in U.S. Pat. No. 4,313,220 entitled CIRCUIT AND METHOD FOR REDUCING POLARIZATION CROSS-TALK CAUSED BY RAINFALL.
Lastly, U.S. Pat. Nos. 3,864,633 and 4,525,861 may be of general relevance.
While certain elements of the present invention may be found in other contexts, insofar as can be determined, none of the relevant literature suggests a low power multiple carrier cellular television system having the efficiency and lack of distortion of the invention set forth in this disclosure.